Isobutylene-nitrosyl chloride



Zentralblatt (1901), II, 1201).

Patented July 5, 1949 UNITED STATES PATENT OFFICE ISOBUTYLENE-NITROSYL CHLORIDE ADDITIO No Drawing. Application April 29, 1948, Serial No. 24,092

6 Claims.

This invention relates to the production of the normally solid adduct of isobutylene and nitrosyl chloride or bromide.

Certain methods for preparing the solid adduct of isobutylene and nitrosyl chloride or bromide are known. For example, it is known to prepare the nitrosyl chloride adduct by adding isobutylone and concentrated hydrochloric acid to wellcooled amyl nitrite (Ipatieif et al., Chemisches This method is also disclosed by Drew and Head, Journal of the Chemical Society (1934), page 49. Another method (U. S. Patent 2,394,430 of February 5, 1946, to Crowder et al.) involves reaction of nitrosyl chloride and excess liquid isobutylene under superatmospheric pressures. The product of the above processes when pure is a colorless solid of empirical formula CHSNOCI melting at about 104 C. Nitrosyl bromide adducts are obtained similarly to nitrosyl chloride adducts.

The chief object of my invention is to accelerate the rate of reaction between nitrosyl chloride or bromide and isobutylene. This object is accomplished by carrying out the reaction in the presence of a catalyst effective for this purpose. Other objects and advantages will appear more fully hereinafter.

The use of a reaction-accelerating catalyst has significant practical advantages for commercial operation. Nitrosyl chloride or bromide is very corrosive toward most construction materials so the material employed in equipment for reactions of nitrosyl chloride or bromide must be relatively expensive. Accordingly, it is advantageous if the reaction rate can be accelerated several-fold since the size of the equipment for a given output of product may then be correspondingly reduced, and the cost of equipment per unit of product thus reduced.

I have found that certain specific adsorptive materials are efiective as catalysts for the reaction of nitrosyl chloride or bromide with isobutylene to form solid isobutylene-nitrosyl chloride or bromide adduct. One of these materials is activated bauxite.

Unlike activated bauxite, certain other adsorptive materials and materials of large surface area which I have tested show little or no effect on the reaction rate.

' The results obtained on addition to the reaction system of activated bauxite will vary with the quantities and quality of the specific activated bauxite used. There are no theoretical upper or lower limits to the proportions of catalyst which are operative in my process but in practice the proportions of catalyst employed will be determined by considerations such as the degree of reaction acceleration desired, the cost of catalyst, etc. Proportions of catalyst which are ordinarily suitable vary from about 0.5 gram of catalyst per mol of nitrosyl chloride reactant to about grams of catalyst per mol of nitrosyl chloride reactant. Usually the proportion of catalyst employed will be in the range from 5 grams to 50 grams of catalyst per mol of nitrosyl chloride reactant.

In the discussion which follows, my invention is described and illustrated with particular reference to the reaction of nitrosyl chloride with isobutylene, but it is to be understood that the same general considerations apply when nitrosyl bromide is employed in the reaction instead of nitrosyl chloride.

The following example illustrates my invention, but is not intended to limit the scope of the invention:

EmampZe.--To 446 grams (about 8 mols) of liquid commercial tank isobutylene of about purity in an all-glass reaction vessel provided with a Dry Ice reflux condenser, a thermometer, a glass stirrer and a Dry Ice-acetone jacketed delivery funnel protected with a drying tube, there were added 12.8 grams of finely ground commercial bauxite, which had been activated at 1200 F. and which was reactivated before use by heating for 41 hours at 200 C.

Then there were added as rapidly as possible from the delivery funnel with stirring about grams (1.53 mols) of commercial nitrosyl chloride which had been freed of impurities (chieiiy nitrogen tetroxide) by fractionation to a boiling point of -6 to 5 C. The mol ratio of free isobutylene:free nitrosyl chloride at the start of this reaction was 5.211. The reaction was allowed to proceed under atmospheric pressure at the reflux temperature of the reaction mixture, which varied from about 0 C. to 7 C. as the composition of the reaction mixture changed during the reaction. 95% of the nitrosyl chloride introduced entered into the reaction after about 1.6 hours (as shown by adding to aqueous sodium hydroxide solution a sample taken from the reaction vessel and analyzing by the Volhard method for chloride ion).

When the reaction of nitrosyl chloride was better than 95% completed, all remaining nitrosyl chloride and isobutylene were allowed to boil out of the vessel through a trap containing aqueous sodium hydroxide solution. The product was Washed out of the vessel with petroleum ether of boiling range 30 C. to 60 C., was washed free of liquid by-product with an additional quantity of the petroleum ether and was air-dried. The yield of adduct thus obtained based on the nitrosyl chloride consumed was 72.3% of theory. The solid product may be further purified and separated from the catalyst by extracting the product from the catalyst with a solvent such as hot benzene and allowing the product to crystallize from solution in the solvent.

When the same procedure was used except that no catalyst was employed the yield of solid adduct on the same basis as above was about 78% of theory and the time required for 95% completion of reaction of the nitrosyl chloride was about 13 hours. The rate of reaction thus was increased about 8 fold by the addition of the catalyst.

In the above example my process is illustrated in terms of batch operation but continuous op eration may also be employed by providing for continuous introduction of the reactants to the reaction vessel and continuous withdrawal of the products. For example, apparatus of the type which comprises an outer tubular reactor down which an inner tubular rotating heat exchange unit passes may be used. This system provides adequate stirring of the reaction mixture but prevents undesirable intermixing of the reaction mixture along the direction of flow.

The use of pure isobutylene in my process is not essential. Thus, the isobutylene may contain other hydrocarbons such as olefins and paraffins normally present in commercial isobutylene. The nitrosyl chloride likewise need not be pure and may, for example, contain about 1 mol percent of impurities likely to be found in commercial nitrosyl chloride such as nitrogen tetroxide and chlorine. However, the presence of an appreciable amount of nitrogen tetroxide, e. g. 10 mol percent or more, in the nitrosyl chloride is undesirable since in the presence of such amounts of nitrogen tetroxide the yield of solid product is small and the crude isobutylenenitrosyl chloride adduct obtained is contaminated with isobutylene-nitrogen tetroxide adduct. The nitrosyl chloride used is likewise preferably kept free of contamination by water since appreciable amounts of water such as 10 mol percent or more in the nitrosyl chloride reduce the yield of solid adduct obtained.

The mol ratio of free liquid isobutylene free nitrosyl chloride in my process is preferably at least 3:1. At and above this mol ratio the reaction temperature may readily be controlled, e. g. by reflux of the reaction mixture, whereas at much lower mol ratios the reaction temperature may be difficult to control and may rise abruptly. Higher mol ratios of free liquid isobutylene free nitrosyl chloride than 3:1 may be used and are used, for example toward the end of a batch or semi-continuous reaction when most of the nitrosyl chloride initially introduced has reacted and a considerable excess of free liquid isobutylene remains in the reaction mixture.

If desired, a solvent inert to the reactants may replace part or all of the excess isobutylene and temperatures may still be adequately controlled, e. g. by reflux.

Temperatures of about -15 C. to C. are well suited for my process; and in the reaction using nitrosyl chloride rather than nitrosyl bromide, especially temperatures between about 12 C. and 6 C. which are the reflux temperatures of isobutylene-nitrosyl chloride mixtures under pressures of about atmospheric, are very suittable for my process. Increasing the temperatures eventually requires operation under more than atmospheric pressures to maintain the reactants liquid, whereas at much lower temperatures the rate of reaction becomes appreciably lower. Temperatures as low as, for example, about 30 C., which may be maintained, for example, by keeping the reaction mixture under reflux at a pressure of about one-third atmosphere, and still lower temperatures are, however, fully operative in my process.

The time allowed for reaction will depend on the degree of completion to be obtained. With at least a 3:1 mol ratio of isobutylene nitrosyl chloride, the rate of reaction is proportional to the concentration of nitrosyl chloride in the liquid reaction mixture and is independent of the isobutylene concentration. At temperatures of about 30 C. the time required for a given degree of reaction is considerably longer than at 6 C.

The solid isobutylene-nitrosyl chloride adduct is conveniently recovered from the liquid byproduct by filtering oflf the solid and washing the solid free of lay-product, e. g. with petroleum ether of boiling range 30 to 60 C. The solid may be extracted away from the catalyst with a solvent, e. g. hot benzene. Dissolved products may be recovered from the solvents by evaporation of any solution removed from the recovery system. If desired, the solid adduct may be recrystallized, e. g. from a weight of benzene about equal to the weight of solid.

I claim:

1. In a process for the production of the solid adduct of isobutylene and a material of the group consisting of nitrosyl chloride and nitrosyl bromide, the improvement which comprises carrying out the reaction between isobutylene and said material in the presence of activated bauxite.

2. A process in accordance with claim 1 in which the reaction temperatures are maintained at about the reflux temperatures of the reaction mixture.

3. A process in accordance with claim 2 in which nitrosyl chloride is employed and the reaction temperatures are between about 15 C. and 0 C. and the vapor pressure over the reaction mixture is about atmospheric.

4. A process in accordance with claim 3 in which the initial mol ratio of free isobutylene free nitrosyl chloride present is at least about 3:1.

5. A process in accordance with claim 1 in which the amount of water introduced into the reaction zone is less than 10 mol percent on the nitroso material introduced into the reaction zone.

6. A process for the production of isobutylenenitrosyl chloride adduct which comprises contacting under about atmospheric pressure nitrosyl chloride at least mol percent pure with activated bauxite and with liquid isobutylene in an initial mol ratio of liquid isobutylene nitrosyl chloride of at least 3:1 while maintaining temperatures between about -15 C. and 0 C.; filtering off solid isobutylene-nitrosyl chloride adduct from the liquid by-products; washing the solid adduct; extracting the solid adduct from the activated bauxite with a solvent; and recovering solid adduct from the solvent.

ANDREW J. MARTIN.

No references cited. 

